explicitly save submission with quiz submissions for rails 3

it was getting saved indirectly through a touch, which no longer
saves in rails 3

Change-Id: Ibeb405fab6de3548d76c92ae7994fd6a7bf99d8a
Reviewed-on: https://gerrit.instructure.com/30691
Tested-by: Jenkins <jenkins@instructure.com>
Reviewed-by: Cody Cutrer <cody@instructure.com>
Product-Review: James Williams  <jamesw@instructure.com>
QA-Review: James Williams  <jamesw@instructure.com>